MagickThresholdImage

Description

Changes the value of individual pixels, (or pixel components/channel(s),
if channel_type parameter is supplied), based on the intensity of each
pixel / pixel component compared to threshold.
The result is a high-contrast, two color image.
Returns TRUE if successful, FALSE if an error occurred.
If the optional channel_type parameter is specified,
MagickThresholdImageChannel() is called on that particular image channel /
pixel component.
channel_type must be a ChannelType constant, one of the following:
MW_RedChannel MW_CyanChannel
MW_GreenChannel MW_MagentaChannel
MW_BlueChannel MW_YellowChannel
MW_AlphaChannel MW_OpacityChannel
MW_BlackChannel MW_IndexChannel
MW_AllChannels